In Emacs, after a lot of editing, I press C-x s (save-some-buffers), then Emacs asks "Save file ...? (y,n,.... d ...)" for each file, I sometimes answer d (diff) to see the changes, but then it's not easy to scroll the diff buffer because the cursor is on the minibuffer. Scrollbar does not work. C-M-v works, but if I try to back-scroll by pressing C-M-- C-M-v, Emacs just says "Type C-h for help". How do I scroll the diff buffer in such cases?